I think you guys are being hyperbolic. All the OP is suggesting is something that gives a bit of variety to the possible PvE decks.
As it stands currently, you take a huge hit to electrum/score gain if you use anything besides a rush.
Another way it could be done is make every additional turn a % multiplier of the original gain, something in the 1%-2% range. For example (using 1%), if I play for 10 turns, I get 10% more electrum than I would have otherwise, whereas if I play for 50 turns I get 50% more. This still leaves it biased towards rush decks, but less so than it is now (FWIW, I would use 2% per turn).